Center rod magnet

ABSTRACT

A pump rotor including a hub defining a major longitudinal axis. A magnet is disposed within the hub along the major longitudinal axis. A plurality of rotor blades project outwardly from the hub away from the longitudinal axis and are spaced apart from one another in a circumferential direction around the longitudinal axis. Each of the plurality of rotor blades define a hydrodynamic bearing at an outer extremity thereof remote from the hub. The plurality of rotor blades define a plurality of flow channels. Each of the plurality of rotor blades is configured to drive a fluid through the flow channels upon rotation of the rotor around the axis.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to and claims priority to U.S. ProvisionalPatent Application Ser. No. 62/508,543, filed May 19, 2017, entitledCENTER ROD MAGNET, the entirety of which is incorporated herein byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

TECHNICAL FIELD

The present invention relates to rotors for use in blood pumps and toblood pumps having such rotors.

BACKGROUND

In certain disease states, the heart lacks sufficient pumping capacityto maintain adequate blood flow to the body's organs and tissues. Forexample, conditions such as ischemic heart disease and hypertension mayleave the heart unable to fill and pump efficiently. This condition,also called congestive heart failure, may lead to serious healthcomplications, including respiratory distress, cardiac asthma, and evendeath. In fact, congestive heart failure is one of the major causes ofdeath in the Western World.

The inadequacy of the heart can be alleviated by providing a mechanicalblood pump, also referred to as a ventricular assist device (“VAD”), tosupplement the pumping action of the heart. VADs may be used to assistthe right ventricle, left ventricle, or both. For example, a VAD mayassist the left ventricle by mechanically pumping oxygenated blood fromthe left ventricle into the aorta.

One form of VAD includes an axial flow pump. In an axial flow pump,blood is transported through a chamber from an inlet to an outlet a pathsubstantially parallel to the axis of rotation of a rotor disposed inthe chamber. The rotor has blades that perform work on the fluid causingit to flow toward the outlet. As shown, for example, in U.S. Pat. No.7,959,551 an axial flow rotor may be supported within the chamber bybearings separate from the rotor itself and driven by stator coilsmounted to the pump and arrayed around the rotor. The stator coilsgenerate a rotating magnetic field that interacts with the rotor torotate the rotor around its axis. Another axial flow blood pump, shownin U.S. Pat. No. 7,934,909 uses a system of multiple magnetic bearingsand hydrodynamic bearings to support and position the rotor within thechamber. These systems require elements in the flow path additional tothe rotor hub and blades. These additional elements can impede the flowof blood through the pump and can cause thrombus to form within thepump.

Another type of blood pump, described in U.S. Pat. No. 7,699,586 (“the'586 Patent), the disclosure of which is hereby incorporated byreference herein, uses a rotor with wide blades having hydrodynamicbearing surfaces on the tip surfaces of the blades. Upon rotation of therotor, the hydrodynamic interaction between the bearing surfaces on thetips of the blade and the chamber wall suspends the rotor in the chamberand maintains the axis of the rotor coaxial with the chamber. Certainembodiments of the rotor shown in the '586 patent have permanent magnetsembedded in the blades of the rotor. These permanent magnets interactwith the rotating magnetic field generated by the stator to spin therotor about its axis. Magnetic interaction between the magnets and aferromagnetic element incorporated in the stator holds the rotor in adesired position along the axis. However, such an arrangement requiresassembly of multiple parts, with precise location of each magnet andprecisely equal magnetization of the individual magnets to preventimbalanced forces on the rotor, which can be challenging. To avoid thesechallenges, some wide-blade axial flow rotors have been made as aunitary body formed of a ferromagnetic material, which has a permanentmagnetization transverse to the rotor's axis. However, the ferromagneticmaterials from which such rotors are made must not only be ferromagneticbut also biocompatible and wear resistant. Materials, such as platinumalloys, that can satisfy both of these requirements are expensive anddifficult to manufacture. Moreover, a magnetic wide-blade rotortypically is made with an even number of blades, most commonly fourblades, to assure balanced operation.

SUMMARY

The present invention advantageously provides for a pump rotor includinga hub defining a major longitudinal axis. A magnet is disposed withinthe hub along the major longitudinal axis. A plurality of rotor bladesproject outwardly from the hub away from the longitudinal axis and arespaced apart from one another in a circumferential direction around thelongitudinal axis. Each of the plurality of rotor blades define ahydrodynamic bearing at an outer extremity thereof remote from the hub.The plurality of rotor blades define a plurality of flow channels. Eachof the plurality of rotor blades is configured to drive a fluid throughthe flow channels upon rotation of the rotor around the axis.

In another aspect of this embodiment, the plurality of rotor blades arenon-ferromagnetic.

In another aspect of this embodiment, the plurality of rotor bladesdefine a collective area at an outer periphery of the rotor remote fromthe hub, and wherein the flow channels define a collective area at theouter periphery, and wherein the collective area defined by theplurality of rotor blades at the outer periphery is greater than thecollective area defined by the flow channels at the outer periphery.

In another aspect of this embodiment, the magnet is a unitary solid andis coaxial with the hub, the magnet being radially magnetized anddefining a plurality of radial poles.

In another aspect of this embodiment, the magnet is cylindrical.

In another aspect of this embodiment, the hub includes tapered endportions and an intermediate portion disposed between the end portions,the intermediate portion houses the magnet and the rotor blades extendfrom the intermediate portion.

In another aspect of this embodiment, the magnet includes neodymium.

In another aspect of this embodiment, the plurality of rotor blades andthe hub are non-ferromagnetic.

In another aspect of this embodiment, the plurality of rotor blades andhub are made from a polymer material.

In another aspect of this embodiment, the plurality of rotor blades andhub are made from a biocompatible material and the magnet includes anon-biocompatible material.

In another embodiment, a blood pump includes a flow chamber defining anaxis. A motor stator having stator coils is disposed about the flowchamber. A rotor includes a hub defining a major longitudinal axis. Amagnet is disposed within the hub along the major longitudinal axis. Aplurality of rotor blades project outwardly from the hub away from thelongitudinal axis and are spaced apart from one another in acircumferential direction around the longitudinal axis. Each of theplurality of rotor blades define a hydrodynamic bearing at an outerextremity thereof remote from the hub. The plurality of rotor bladesdefine a plurality of flow channels. Each of the plurality of rotorblades is configured to drive a fluid through the flow channels uponrotation of the rotor around the axis. The stator coils are configuredto generate a magnetic field within the flow chamber rotating about theaxis of the flow chamber. The rotating magnetic field interacts with themagnet of the rotor to drive the rotor about the axis thereof.

In another aspect of this embodiment, the motor stator includes aback-iron and wherein the magnet and back-iron are passively attractedto each other and cooperate to restrain the rotor from axialdisplacement within the flow chamber during operation.

In another aspect of this embodiment, the magnet is enclosed within therotor.

In another aspect of this embodiment, the magnet is sealed within therotor.

In another aspect of this embodiment, the plurality of rotor blades arenon-ferromagnetic.

In another aspect of this embodiment, the plurality of rotor bladesdefine a collective area at an outer periphery of the rotor remote fromthe hub, and wherein the flow channels define a collective area at theouter periphery, and wherein the collective area defined by theplurality of rotor blades at the outer periphery is greater than thecollective area defined by the flow channels at the outer periphery.

In another aspect of this embodiment, the magnet is a unitary solid andis coaxial with the hub, the magnet being radially magnetized anddefining a plurality of radial poles.

In another aspect of this embodiment, the plurality of rotor blades andhub are made from a polymer material.

In another aspect of this embodiment, the plurality of rotor blades andhub are made from a biocompatible material and the magnet includes anon-biocompatible material.

In yet another embodiment, a method of operating a blood pump includesgenerating a rotating magnetic field configured to rotate a rotor of theblood pump. The rotor includes a hub and a magnet disposed within thehub.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of a rotor according to an embodiment ofthe present disclosure;

FIG. 2 is an elevational view of the rotor of FIG. 1;

FIG. 3A is a front view of the rotor of FIG. 1;

FIG. 3B is a sectional view taken along line B-B of FIG. 3A;

FIG. 3C is a sectional view taken along C-C of FIG. 2;

FIG. 4 is an exploded view of the rotor of FIG. 1;

FIG. 5 is a schematic sectional view of a pump according to anembodiment of the disclosure including the rotor of FIG. 1;

FIG. 6 is a perspective view of a rotor according to another embodimentof the present disclosure;

FIG. 7 is an exploded view of the rotor of FIG. 6; and

FIG. 8 is a partially schematic view of a rotor according to anotherembodiment of the present disclosure.

DETAILED DESCRIPTION

As used in this disclosure, the term “generally helical” refers to afeature which extends in the direction parallel to an axis and whichcurves in the circumferential direction around the axis over at least50% of its extent in the direction along the axis. Also, as used herein,the terms “about” and “substantially” are intended to mean that slightdeviations from absolute are included within the scope of the term somodified.

Referring now to the drawings in which like reference designators referto like elements, there is a shown in FIGS. 1-4 a rotor or impeller 10constructed in accordance with one embodiment of the present disclosure.Rotor 10 includes a hub 20, a plurality of rotor blades 30, and a magnet40. Hub 20 defines a central body of rotor 10 and also defines a rotoraxis or major longitudinal axis 14 about which rotor 10 rotates. Hub 20includes end portions 24, 26 and an intermediate portion 22 disposedbetween end portions 24 and 26. The end portions 24, 26 are taperedsolids of revolution, and intermediate portion 22 is substantially inthe form of a body of revolution which may have a uniformcross-sectional dimension along its length, or which may vary incross-sectional dimension. In this regard, intermediate portion 22 maybe cylindrical, and end portions 24 and 26 may be conical as isdepicted. Intermediate portion 22 is hollow and includes a sidewall 21that defines an interior space surrounded by a wall surface 29 in theform of a surface of revolution about axis 14. As best shown in FIG. 3B,such interior space is sized to receive and house magnet 40.

The plurality of rotor blades 30 project from the hub 20. In theparticular embodiment depicted, the plurality of blades 30 includesexactly three rotor blades 30 a-c. Each blade 30 extends outwardly fromhub 20 away from hub axis 14 to an outer extremity thereof remote fromhub 20. More particularly, each blade 30 extends out of hub 20 in anoutward radial or “spanwise” direction perpendicular to the axis 14.Each blade 30 also extends in a lengthwise or axial direction over aportion of the axial extent of hub 20 so that blades 30 a-c arecoextensive with one another in the axial direction. In the particularembodiment depicted, each blade 30 extends along the length ofintermediate portion 22 and terminates adjacent end portions 24 and 26of hub 20. In other words, blades 30 a-c project outwardly fromintermediate portion 22. However, in some embodiments, blades 30 a-c maypartially project outwardly from end portions 24 and 26 as well as fromintermediate portion 22.

Each blade 30 defines generally helical surfaces 36, 38 that intersectthe outer surface or floor surface 23 of intermediate portion 22 of hub20. These helical surfaces 36, 38 are referred to as a pressure surface36 and a suction surface 38, as shown in FIG. 3C. The pressure andsuction surfaces 36, 38 are disposed at opposite sides of each blade 30and converge with each other at inflow and outflow edges 37, 39 whichare disposed at inflow and outflow ends of blades 30 a-c. Pressuresurface 36 faces forward, i.e., the circumferential direction in whichthe rotor spins as indicated by arrow F in FIG. 1, and suction surface38 faces rearward, i.e., the circumferential direction opposite theforward direction. The arrow D in the drawings indicates the directionof flow from upstream to downstream.

Rotor blades 30 a-c are evenly spaced apart from one another around axis14 in forward and rearward circumferential directions. Thus, blades 30a-c define a plurality of flow channels 12 that extend between blades 30a-c and likewise in an axial direction along rotor axis 14. Suchchannels 12 are bounded by outer surface 23 of intermediate portion 22and the pressure and suction surfaces 36, 38 of adjacent blades 30. Inthis regard, flow channels 12 are generally helical to correspond to thehelical profile of pressure and suction surfaces 36 and 38.

Each blade 30 has a tip surface 35 intersecting with and extendingbetween the pressure surface and suction surface 36, 38. Each tipsurface 35 faces outwardly away from axis 14 and defines the outermostextremity or outer periphery of both blade 30 and the rotor 10 itself.These tip surfaces 35 define a collective surface area that is largerthan a collective area defined by flow channels 12 at the outerperiphery of rotor 10. In other words, each tip surface 35 of blades 30a-c is large as compared to empty space of flow channels 12 such that inthe aggregate, the surface area defined by tip surfaces 35 is moreextensive than the aggregate area of flow channels 12 taken at theperiphery of rotor 10. In this regard, rotor 10 is characterized as awide-blade or large-area rotor. Other exemplary wide-blade rotors aredescribed in the heretofore referenced '586 Patent; U.S. Pat. Nos.7,972,122; 8,007,254; 8,419,609 and U.S. Publication No. 2015/0051438,the entirety of which are all incorporated by reference herein. Thewide-blade configuration of rotor 10 allows rotor blades 30 a-c to havehydrodynamic bearing surfaces at blade tips 35 that are capable ofsuspending rotor 10 within a pump housing during operation without theneed for mechanical supports. Also, such a wide-blade configuration ofrotor 10, particularly in combination with hydrodynamic bearings atblade tips 35, allows it to be extraordinarily compact. For example, themaximum diameter of rotor 10 at blades 30 a-c may be about 0.5 inches(12.7 mm) and have an overall length of about 0.86 inches (21.8 mm).

In the configuration shown in FIGS. 1 and 2, each tip surface 35 ofrotor blades 30 a-c includes a land surface 33, an upstream hydrodynamicbearing surface 34 and a downstream hydrodynamic bearing surface 32.Land surface 33 is in the form of a part of a surface of revolutionaround central axis 14. In the particular embodiment depicted, thesurface of revolution is a circular cylinder so that the radius fromaxis 14 to a land surface 33 is uniform over the entire extent of rotor10 and so that this radius is one-half the maximum diameter of rotor 10at blades 30.

Each hydrodynamic bearing surface 32, 34 extends in the rearwardcircumferential direction from pressure surface 36 of its respectiveblade 30 and is bounded by and recessed radially relative to landsurface 33. The recess of bearing surfaces 32, 34 is at a maximum at theforward edge of such surfaces where bearing surfaces 32, 34 meetpressure surface 36 of the blade 30. The recess of each bearing surface32, 34 diminishes progressively in the rearward circumferentialdirection, so that each bearing surface 32, 34 merges smoothly into landsurface 33 at the rearward edge of each bearing surface 32, 34.

Referring now to FIGS. 3 and 4, in one configuration, magnet 40 is apermanent magnet and is a unitary solid of revolution. In this regard,magnet 40 may be a solid cylinder in which it is completely solidthrough its thickness, as shown. However, magnet 40 can also be anelongate tube with a hollow interior. Magnet 40 is sized to fit and beretained within the interior space of hub 20. In addition, magnet 40 ismagnetized with a magnetic field direction transverse to its axis, anddesirably perpendicular to its axis so as to have a plurality of radialpoles. The magnet and has sufficient magnetic flux to rotate rotor 10when a moving magnetic field is applied to such poles. In oneconfiguration, magnet 40 is the only component having ferromagneticproperties within rotor 10, which simplifies the construction of rotor10. Magnet 40 can be made from any magnetic material includingnon-biocompatible materials and biocompatible materials. For example,magnet 40 may be made from neodymium and alloys thereof, oraluminum-cobalt-nickel alloys.

As best shown in FIG. 3B, magnet 40 is disposed within intermediateportion 22 of hub 20 and fixed thereto so that the axis of the magnet40, and hence its center of mass, is aligned with the axis 14 of therotor 10. Magnet 40 also extends from one end of intermediate portion 22to the other end and terminates just short of end portions 24 and 26.However, in some embodiments, magnet 40 may extend into the end portions24, 26. In addition, magnet 40 is disposed within hub 20 so that magnet40 is aligned with rotor blades 30 a-c in the axial direction and isgenerally coaxial with axis 14.

Magnet 40 is a permanent magnet made from ferromagnetic materials thatmay or may not be biocompatible. However, the biocompatibility magnet 40is of no import when implanted within a patient because such magnet 40is embedded within rotor 10 which itself has a biocompatible exterior.In addition to having a biocompatible exterior, rotor 10 isnon-ferromagnetic. As discussed above, magnet 40 may be the onlymagnetic component within rotor 10. In other words, hub 20 and rotorblades 30 a-c are made from non-ferromagnetic materials and are eithermade from a biocompatible material or made from a non-biocompatiblematerial with a biocompatible coating. For example, rotor 10 may be madefrom a biocompatible polymer material, such as silicone polymers,fluoroalkylsiloxane polymers or polyphosphazenes. Such polymer materialcan be molded over magnet 40. Alternatively, a polymeric rotor 10 can bemolded separately from magnet 40 and machined so as to form the interiorspace within hub 20 for magnet 40. A separately molded end portion 24,such as that shown in FIG. 4, may then be welded, such as by frictionwelding, or otherwise fixed to intermediate portion 22 to seal magnet 40therein.

Rotor 10 can also be made from non-ferromagnetic metals, such asnonmagnetic stainless steel or titanium, or non-ferromagnetic ceramics,such as pyrolytic carbon, aluminum oxide, and zirconium oxide, forexample. Furthermore, rotor 10 may have a biocompatible coating, such asa parylene, silicone, chromium nitride, or titanium nitride coating, forexample. Rotor 10 can be made from a combination of the materialsdescribed above, but overall the rotor itself, regardless of thematerials selected, is non-ferromagnetic. In this regard, the selectionof materials is numerous and can be selected to control costs and/oroptimize performance without the additional concern of providingmagnetization as such is provided by center magnet 40.

A pump 50 according to one embodiment of the present invention includesa pump housing 60, motor stator 70, and rotor 10 as discussedhereinabove with reference to FIGS. 1-4. Housing 60 defines an interiorbore or flow channel 62. Rotor 10 is disposed within flow channel 62 andan interior surface 64 of housing 60 surrounds tip surfaces 35 of rotor10. The motor stator 70 is disposed around the exterior of housing 60.Rotor blades 30 a-c are disposed directly between motor stator 70 andmagnet 40. Motor stator 70 includes a set of coils 72 that are arrayedaround the exterior of housing 60. Coils 72 may be of conventionalconstruction. By way of example, coils 72 may be provided as three setsof diametrically opposed coils disposed at equal spacing around thecircumference of housing 60. Motor stator 70 also includes aferromagnetic component, referred to as a back-iron, which is associatedwith stator coils 72.

In operation, with pump 50 implanted in the body of mammalian subject,and with housing 60 connected into the circulatory system, for example,in the conventional manner for a VAD, coils 72 are actuated to provide amagnetic field directed transverse to rotor axis 14 to cause such fieldto rotate rapidly around axis 14. Such magnetic field interacts with theradial poles of magnet 40 disposed within rotor 10 to rotate magnet 40and, consequently, rotor 10 itself along with the magnetic field.

Rotor 10 also passively interacts with back-iron 74 of motor stator 70.In this regard, the permanent magnetism of back-iron 74 and centermagnet 40 results in a magnetic attraction that resists axialdisplacement of rotor 10 within flow channel 62 that may be caused bypressure head gravity, or both. Also, while rotor 10 is rotated, a thinfilm of blood between hydrodynamic bearing surfaces 32, 34 and interiorsurface 64 of housing 60 is formed which maintains rotor 10 coaxial withhousing 60 so that rotor 10 does not contact interior surface 64 due toradial movement, transverse to the axis 14 of rotor 10, or due totilting of axis 14 relative to housing 60. Thus, hydrodynamic bearings32, 34 of blades 30 a-c in conjunction with the axial alignment providedby the attraction of center magnet 40 and back-iron 74 eliminate theneed for mechanical suspension systems to stabilize rotor 70 duringoperation. This allows flow channel 62 to be free and clear ofobstructions other than rotor 10 itself.

The rotor 10 as discussed above offers significant advantages. Forexample, because the blades 30 of the rotor 10 are formed fromnon-ferromagnetic materials, the blades 30 do not introduce imbalancedmagnetic forces, and the rotor 10 can operate stably with three blades30. A rotor 10 with three blades 30 and three channels having a givenaggregate cross-sectional area, provides better flow conditions than acomparable four bladed rotor with four channels having the sameaggregate cross-sectional area. Precise alignment between the axis ofthe magnet 40 and the axis 14 of the rotor is achieved in commonmanufacturing techniques. For example, the magnet can be formed to abody of revolution of precise dimensions by techniques such as machiningor centerless grinding. The interior surface 29 of the wall surroundingthe interior space can be formed to a surface of revolution havingprecise dimensions and precisely coaxial with the axis and with the landsurfaces 33 of the blades, by machining or molding the interior surface.

Other alternative embodiments of the aforementioned devices arecontemplated. For example, FIGS. 6 and 7 depict an alternativeembodiment rotor 110. Such rotor 110 is similar to rotor 10 in that itincludes a hub 120, a center magnet 140 disposed within an intermediateportion 122 of hub 120, and a plurality of wide-blades 130 that definehydrodynamic bearing surfaces 132, 134 and flow channels 112 betweensuch blades 130. Moreover, just as with rotor 10, the only magneticcomponent in rotor 110 is center magnet 140. However, rotor 110 differsin that it includes four rotor blades 130 a-d, rather than three. Inthis regard, a center magnet, such as magnets 40 and 140, in conjunctionwith non-ferromagnetic blades, such as blades 30 or 130, allows anynumber of rotor blades to be utilized without concern that the number ofblades selected would affect magnetic balancing.

Another rotor 210 is shown in FIG. 8 according to a further embodimentof the present disclosure. Rotor 210 is similar to rotor 10 in that itincludes a hub 220, rotor blades 230 (shown in phantom lines) extendingfrom hub 220, and a center magnet 240. Such rotor blades 230 may benon-ferromagnetic and also have hydrodynamic bearing surfaces at theirtips, as described above. As shown, hub 220 has a hollow intermediateportion 222 disposed between end portions 224 and 226. Intermediateportion 222 includes a first section 222 a and a second section 222 bthat each partially define an interior space of hub 220. In this regard,first section 222 a includes a first wall surface 229 a in the form of asurface of revolution about rotor axis 214, and second section 222 bincludes a second wall surface 229 b also in the form of a surface ofrevolution about rotor axis 214. Such surfaces 229 a-b surround anddefine the interior space. In the particular embodiment depicted, firstand second wall surfaces 229 a-b define the interior space such thatinterior space has a uniform cross-sectional dimension along first wallsurface 229 a and a tapering cross-sectional dimension along second wallsurface 229 b. However, in other embodiments, first and second wallsurfaces 229 a-b may define the interior space such that the interiorspace has a tapering cross-sectional dimension along both the first andsecond wall surfaces 229 a-b but where the cross-sectional dimension ofthe interior space tapers at a greater rate along second wall surface229 b than first wall surface 229 a. It is also contemplated thatintermediate portion 222 of hub 220 may have a single wall surface ofrevolution that defines an interior space that tapers along its entirelength so as to form a frustoconical space, for example.

In the rotor embodiment depicted in FIG. 8, magnet 240 may have smallerbut proportional dimensions relative to that of intermediate portion 222such that magnet 240 can be disposed in the interior space defined bysurfaces 229 a-b and so that an axis defined by magnet 240 is coaxialwith axis 214. Thus, magnet 240, may be a unitary solid of revolution inwhich a first section 242 a thereof has a first cross-sectionaldimension proportional to first section 222 a of hub 220 and a secondsection 242 b thereof has a second cross-sectional dimensionproportional to second section 222 b of hub 220.

In the embodiments discussed above, the rotor is constrained againstaxial movement relative to the pump chamber by magnetic attractionbetween the magnet and the back-iron incorporated in the stator. Inother embodiments, the hydrodynamic bearing surfaces of the rotor mayinclude hydrodynamic bearing surfaces arranged to provide axial thrustand thus constrain the rotor against axial movement relative to the pumpchamber and stator. For example, as disclosed in U.S. Published PatentApplication No. 2011/0311383, the entirety of which is incorporated byreference herein, hydrodynamic bearing surfaces facing in a directionoblique to the axis may be provided on the blades so as to provide axialthrust in one direction. To provide full axial constraint, the obliquesurfaces may include oblique surfaces facing in opposite axialdirections.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as described in the claims below.

What is claimed is:
 1. A pump rotor, comprising: a hub defining a majorlongitudinal axis; a magnet disposed within the hub along the majorlongitudinal axis; and a plurality of rotor blades projecting outwardlyfrom the hub away from the longitudinal axis and being spaced apart fromone another in a circumferential direction around the longitudinal axis,each of the plurality of rotor blades defining a hydrodynamic bearing atan outer extremity thereof remote from the hub, the plurality of rotorblades defining a plurality of flow channels, each of the plurality ofrotor blades being configured to drive a fluid through the flow channelsupon rotation of the rotor around the axis.
 2. The rotor of claim 1,wherein the plurality of rotor blades are non-ferromagnetic.
 3. Therotor of claim 1, wherein the plurality of rotor blades define acollective area at an outer periphery of the rotor remote from the hub,and wherein the flow channels define a collective area at the outerperiphery, and wherein the collective area defined by the plurality ofrotor blades at the outer periphery is greater than the collective areadefined by the flow channels at the outer periphery.
 4. The rotor ofclaim 1, wherein the magnet is a unitary solid and is coaxial with thehub, the magnet being radially magnetized and defining a plurality ofradial poles.
 5. The rotor of claim 4, wherein the magnet iscylindrical.
 6. The rotor of claim 1, wherein the hub includes taperedend portions and an intermediate portion disposed between the endportions, the intermediate portion houses the magnet and the rotorblades extend from the intermediate portion.
 7. The rotor of claim 1,wherein the magnet includes neodymium.
 8. The rotor of claim 1, whereinthe plurality of rotor blades and the hub are non-ferromagnetic.
 9. Therotor of claim 1, wherein the plurality of rotor blades and hub are madefrom a polymer material.
 10. The rotor of claim 1, wherein the pluralityof rotor blades and hub are made from a biocompatible material and themagnet includes a non-biocompatible material.
 11. A blood pump,comprising: a flow chamber defining an axis; a motor stator havingstator coils disposed about the flow chamber; and a rotor including: ahub defining a major longitudinal axis; a magnet disposed within the hubalong the major longitudinal axis; and a plurality of rotor bladesprojecting outwardly from the hub away from the longitudinal axis andbeing spaced apart from one another in a circumferential directionaround the longitudinal axis, each of the plurality of rotor bladesdefining a hydrodynamic bearing at an outer extremity thereof remotefrom the hub, the plurality of rotor blades defining a plurality of flowchannels, each of the plurality of rotor blades being configured todrive a fluid through the flow channels upon rotation of the rotoraround the axis; the stator coils being configured to generate amagnetic field within the flow chamber rotating about the axis of theflow chamber, the rotating magnetic field interacting with the magnet ofthe rotor to drive the rotor about the axis thereof.
 12. The pump ofclaim 11, wherein the motor stator includes a back-iron and wherein themagnet and back-iron are passively attracted to each other and cooperateto restrain the rotor from axial displacement within the flow chamberduring operation.
 13. The pump of claim 11, wherein the magnet isenclosed within the rotor.
 14. The pump of claim 13, wherein the magnetis sealed within the rotor.
 15. The pump of claim 11, wherein theplurality of rotor blades are non-ferromagnetic.
 16. The rotor of claim11, wherein the plurality of rotor blades define a collective area at anouter periphery of the rotor remote from the hub, and wherein the flowchannels define a collective area at the outer periphery, and whereinthe collective area defined by the plurality of rotor blades at theouter periphery is greater than the collective area defined by the flowchannels at the outer periphery.
 17. The rotor of claim 11, wherein themagnet is a unitary solid and is coaxial with the hub, the magnet beingradially magnetized and defining a plurality of radial poles.
 18. Therotor of claim 11, wherein the plurality of rotor blades and hub aremade from a polymer material.
 19. The rotor of claim 11, wherein theplurality of rotor blades and hub are made from a biocompatible materialand the magnet includes a non-biocompatible material.
 20. A method ofoperating a blood pump, comprising: generating a rotating magnetic fieldconfigured to rotate a rotor of the blood pump, the rotor including ahub and a magnet disposed within the hub.